CRUSTACEA. 
211 
plate as is characteristic of the genus Creusia. A single conspicuous furrow, 
slightly witliin and concentric with the margin, may indicate the line of 
contact of the capitulum with the walls of the basis. 
Basis tuhuliform, sub-cylindrical or cup-shaped. 
The specimen is attached to a colony of Favosites hemisphericus and has at 
some time been overgrown as far as the aperture by the multiplication of 
the cell tubes. A portion of the coral was subsequently removed by natural 
causes, exposing the capitulum, but leaving the tubular basis completely 
enveloped. The surface of the former still bears traces of the cell walls 
of the coral. By removal of a portion of the coral near the side of the 
specimen it is found that the internal cavity is partially filled with soft 
decomposed chert, the remainder of the cavity filling, the capitulum and the 
entire coral being silicified. The internal plates, scutum and tergum, are not 
preserved. 
Dimensions. The capitulum has a length of 10 mm., and a width of 
8.5 mm. The depth of the tubular basis can be measured through the 
aperture for 8 mm., but is probably somewhat greater. 
Observations. This interesting species brings to our knowledge a representa¬ 
tive, from Devonian rocks, of forms included under the recent genera Pyrgoma 
and Creusia, neither of them previously recognized in palaeozoic formations, and 
the latter not heretofore known among fossils. Features of distinctively generic 
value in which this species differs from recent members of the genus Creusia 
are not readily apparent, and, therefore, the term Palmcreusia is used tenta¬ 
tively to express the probability that such differences will eventually be 
found. 
Distribution. Corniferous limestone. LeRoy, Genesee county. 
